Preparation And Corrosion Resistance Of FeCoNiCr High Entropy Alloy Coatings

Different from the design concept of traditional alloys,high-entropy alloys have many principal components,high configurational entropy,and tend to form simple solid solution structures such as face centered cubic,body centered cubic,and even amorphous phase.In addition,high entropy alloys exhibit unique structural and mechanical properties due to the interaction of various elements,such as good corrosion resistance and wear resistance.Therefore,it has become a hot research issue in recent years.At present,many scholars have studied the high entropy alloys,among which arc melting and mechanical alloying are the more mature methods,but there are few researches on the preparation of high entropy alloys by electrodeposition.In this thesis,FeCoNiCr high-entropy alloy was prepared by electrodeposition.The main salt concentration and process parameters were optimized by orthogonal test,and the optimal formula and process parameters were obtained.FeCoNiCr high-entropy alloy was electrodeposited on the surface of copper matrix,and a smooth and bright coating was obtained.In addition,its mechanical properties,microstructure,morphology,composition and corrosion resistance were tested by means of microhardness tester,X-ray diffractometer,field emission scanning electron microscope,energy spectrometer and electrochemical workstation.The best formulations for electrodeposited FeCoNiCr high-entropy alloy coatings were obtained:2 g/L ferrous sulfate,4 g/L cobalt sulfate,20 g/L nickel sulfate,200 g/L chromium sulfate,25 g/L boric acid,75 g/L potassium chloride,92 g/L citric acid,48 g/L sodium citrate,1 g/L sodium hypophosphite.Process parameters:current density of25A/dm²,temperature of 25℃,pH value of 2.5.Under the best experimental conditions,an amorphous FeCoNi Cr high-entropy alloy coating with a bright surface,uniform composition,and only a few micro-cracks can be obtained,and the hardness can reach466.49 HV.The bonding force test and the electrochemical performance test were carried out.The experimental results showed that the coating laryer had good bonding strength with the substrate and good corrosion resistance.In 3.5 wt.%NaCl solution,the self-corrsion potential is-0.45 V,and the self-corrosion current density is 1.73×10^-6 A/dm².The corrosion mechanism is pitting caused by the depolarization of oxygen and chloride ions;The self-corrsion potential in an acidic solution of 1 mol/L H₂SO₄ is-0.33 V,and the self-corrosion current density is 1.25×10^-5 A/dm².The corrosion mechanism is uniform corrosion caused by depolarization of hydrogen;The self-corrsion potential in 1 mol/L NaOH is-0.74 V,and the self-corrosion current density is 1.38×10^-6 A/dm².The corrosion mechanism is uniform corrosion caused by oxygen absorption.